1. Field of the Invention
The present invention relates to a clutch cover assembly for a dual clutch disc clutch mechanism and particularly to a clutch cover assembly which has a wear compensation mechanism to compensate for wear of the friction facings and to maintain a generally constant biasing pressure from a diaphragm spring and corresponding pressure plate on the clutch discs throughout the useful life of the mechanism regardless of the wear of the friction facings on the clutch discs. The present invention further relates to a clutch cover assembly which has an abrasion mechanism to assist in maintaining the generally constant biasing pressure from a diaphragm spring and corresponding pressure plate on the clutch discs throughout the useful life of the mechanism regardless of the wear of the friction facings on the clutch discs
2. Description of the Related Art
A clutch cover assembly of a clutch device is installed to a flywheel of the engine. Friction facings of the clutch disk assembly are selectively pressed against the flywheel by spring force of a diaphragm spring. Thus, a torque of the engine is transmitted to the transmission side. When the wear amount of the friction facings is above a specified amount in the clutch device, the friction facings can not be used or the pressing load changes because a posture of the diaphragm spring of the clutch covers changes. As the result, the clutch disk assembly has to be exchanged for a new one. Therefore, there is a demand for a clutch disk with a longer life span.
In order to achieve a long life span of the clutch, it is important to increase the available thickness of the friction facings of the clutch disk assembly. For the purpose, the friction facings are fixed to a cushioning plate without using rivets, etc.
In a clutch cover assembly, when the friction facings is worn, in order to extend the life of the clutch disk, it is necessary to restore a diaphragm spring to the initial position for better contact with the friction facing. For that purpose, the wear amount needs to be determined, and depending on the wear amount, members which support a diaphragm spring (a fulcrum ring of a pressure plate side, or a supporting mechanism of a clutch cover side) are sometimes made to be adjustable. Once adjusted, the life of friction facings of a clutch disk assembly can be extended.
A wear compensation mechanism of the clutch cover assembly includes mainly a fulcrum ring disposed between a clutch cover and a diaphragm spring, an urging mechanism to urge a fulcrum ring away from a pressure plate and a regulating mechanism not only to prevent a fulcrum ring from becoming dis-engaged from a pressure plate but also to permit a fulcrum ring to move away from the pressure plate in an axial direction corresponding to the wear amount of the friction facings as they become worn.
The regulating mechanism is installed inside the pressure plate. An open portion is formed in the pressure plate on the side opposite to the friction facings, a friction bush is installed, and inside the bush a wear sensor member is installed. The wear sensor member, which prevents a fulcrum ring from moving toward the clutch cover side, is connected not only with the friction bush by a friction force but also with the clutch cover so as not to move toward the friction facings side.
When the friction facings is worn, the pressure plate moves so as away from the friction sensor connected with the clutch cover. As the result, a space is formed between the wear sensor member and the fulcrum ring corresponding to the wear amount. Then, when releasing the clutch, the fulcrum ring moves toward the sensor member until touching it by the urging mechanism. As the result, the posture of the diaphragm spring is kept generally the same as wear occurs.
The above described conventional wear compensation mechanism has a friction-connecting member between a wear sensor member and a friction bush inside the pressure plate. Therefore, the friction-connecting member tends to be affected by heat transmitted from the friction face of the pressure plate. As the result, the frictional resistance caused at the friction-connecting member is not stable.
When a vigorous vibration is caused during engaging the clutch, under adjustment sometimes occurs. Under adjustment is a phenomenon that, when the pressing part presses the fulcrum ring in an axial direction in engaging the clutch and the force is applied in an axial direction from the first inclined faces of the wedge mechanism to the second inclined faces, the wedge part slides toward the original position because of the increased force applied in a circular direction to the wedge part with the second inclined faces. Under such a condition the location of the fulcrum ring does not compensate for all of the wear.
One way to prevent the under adjustment is to decrease an inclining angle of the first and second inclined faces. Since the component in a circular direction of the force applied in an axial direction to the wedge part decreases, the wedge part hardly slides to the initial position. However, when the inclining angle decreases, over adjustment tends to happen occur where the wedge moves too much in a circular direction and moves the fulcrum ring in an axial direction more than the wear amount. Therefore, decreasing the inclining angle is not desirable.